At some point, every investor will be looking at some shocking loss in his or her portfolio. For the Fool's Austin Smith, it was SUPERVALU, a company that he thought was too cheap to ignore but that promptly crashed after he'd purchased shares. Rather than have faith in his research and conviction, he backed out of the position and sold at a sharp loss. From that point forward, shares have doubled. 

The following video below shares the shocking outcome from two model portfolios -- one that assumed investors sold their biggest losers, as Austin did, and another that assumed they had the conviction to double down on those stocks. 

While no portfolio grows at this modeled linearity, and you may be closer or further away from retirement, the principle of the story remains the same: If you still have a high level of conviction in your research and the market hasn't agreed with you over the short run, be patient. Mr. Market can be irrational, and in the short run there's a disconnect between a company's true value and what is reflected in the share price.